1. Field of the Invention
This invention relates generally to a method for plasma deposition of silicon, and, more specifically, relates to a high-temperature method for plasma deposition of silicon wherein thermal deposition is largely suppressed.
2. Description of the Prior Art
In the paste, plasma deposition of silicon has been effected at high temperatures in order to control the characteristics of the deposited film. The state of the art in plasma processing is described in Solid State Technology, April 1978, pp 89-126. Specific methods and details of a plasma deposition system are to be found in the Engle U.S. Pat. No. 4,223,048 issued, Sept. 16, 1980. When plasma deposition is effected in a high temperature ambient, however, there is a tendency to induce thermal decomposition of the silicon source gas, whereby deposition takes place not only on the workpieces but also throughout the heated portions of the deposition system. An additional undesirable feature of the thermal decomposition is that thermal inhomogeneity engenders non-uniform deposition.
Recent requirements in the fabrication of semiconductor wafers have mandated very close thickness and compositional control over scores of workpieces in a single deposition cycle. Thus, not withstanding the developments of the past, a need continues to exist for improved control of the deposition of silicon and polysilicon. Furthermore, for plasma deposition of conducting films, a need continues to exist for a deposition method whereby thermal deposition is inhibited on the necessarily insulative portions of the deposition system.